Patients with a history of anaphylaxis, urticaria or rash occurring immediately after penicillin therapy are at an increased risk of immediate hypersensitivity to penicillins and other related antibiotics (beta-lactams) and should not receive a beta-lactam antibiotic.
A non-penicillin beta-lactam antibiotic may be considered for patients who develop a non-severe delayed rash when treated with a penicillin.
All penicillins contain a beta-lactam ring but not all beta-lactams are penicillins!
Other beta-lactam antibiotics are cephalosporins, carbapenems and monobactams (aztreonam).
Approximately 10% of patients who are truly allergic to penicillin will also be hypersensitive to other beta-lactams such as cephalosporins (e.g. cefuroxime, ceftazidime)
Cross sensitivity to carbopenems can also occur (e.g. imipenem, meropenem).
Augmentin®, Timentin® and Tazocin® contain penicillin.
Anaphylaxis is a rare but life-threatening systemic reaction that develops rapidly (5-30 minutes) and is antibody (IgE) mediated.
Urticaria and angioedema (also IgE-mediated) are more common reactions but less severe.
Maculopapular rashes are the most common allergic reaction but are not life threatening.
Gastro-intestinal upset (ie diarrhoea and/or vomiting) caused by penicillin is not an allergy - it's a side effect!
Beta-lactam hypersensitivity is a caution / contra-indication to potentially life-saving agents so establishing and documenting the type of allergic reaction is paramount.
Refer to Traffic light chart for safety of antibiotics in penicillin allergic patients.